Electric cables and condenser insula-



United States Patent ()fifice Re. 25,187 Reissued June 19, 1962 ELECTRIC CABLES AN D CONDENSER INSULA- TION INCLUDING WAX AND PETROLATUM Geofirey Ernest Bennett, Crayford, England, assignor to Dussek Brothers & Company Limited, Crayford, England, a British company No Drawing. Original No. 2,867,596, dated Jan. 6, 1959,

Ser. No. 445,937, July 26, 1954. Application for reissue Nov. 23, 1959, Ser. No. 854,986 Claims priority, application Great Britain Aug. 13, 1953 15 Claims. (Cl. 260-27) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The invention is for improvements in or relating to electric cables and condensers and has particular reference to impregnating compositions for use in the manufacture of cables and condensers in which the dielectric consists of fibrous material, for example paper tape, impregnated with an insulating composition.

It is an object of the present invention to provide a cable or condenser impregnating composition having good non-migratory properties and which may, accordingly, be used in any situation where compound migration of the impregnant could cause trouble.

I [We] have now found that petrolatum may be used as the basis of the impregnating composition in the place of the insulating oil.

According to the present invention there is provided a composition for the impregnation of fibrous material for the insulation of the conductors of cables or condensers which composition comprises petrolatum containing from 3% to 50% by weight on the weight of the final composition of a synthetic hydrocarbon wax of melting point above 85 C. and of low dielectric loss, with [or without] polyisobutylene and/or polyethylene. The synthetic hydrocarbon wax preferably has a melting point between 85 and 120 C., and is preferably employed in a proportion of from 10% to 30% by weight on the Weight of the final composition.

An example of a suitable synthetic Fischer Tropsch hydrocarbon wax is that known under the trade name Super Hard Wax No. 105, which wax has a melting point of 108/110 C. [and is a product of the Fischer Tropsch process This wax has an average molecular weight of about 600 corresponding to C and its boiling point under vacuum is above 460 C. [A further example of a suitable synthetic wax is a synthetic wax produced by the hydrogenation of less saturated naturally occurring hydrocarbons. A still further example of a suitable synthetic wax is a polyethylene wax known under the trade name A1cowax.]

The proportion of polyisobutyle-ne and/ or polyethylene in the impregnating composition, when employed, will depend upon the molecular weight of the polymer. Thus when low molecular weight polyisobutylene and/ or polyethylene are used, e.g. polyisobutylene of approximate molecular weight 1200 known as Oronite 32, or Polythene Grade 200,000 of approximate molecular Weight 2500, a proportion of up to 40% of the polymeric material by weight on the weight of the final composition may be used. When high molecular weight polyisobutylene and/or polyethylene are employed, e.g. polyisobutylene of approximatemolecular weight 100,000 the proportion of the polymeric material should not, in general, exceed 10% by weight on the weight of the final composition.

There may be included in the composition a proportion of up to 40% by weight on the weight of the final composition of petroleum wax, rosin or other resins of low dielectric loss. Oxidation inhibitors, for example,

phenyl B naphthylamine, and metal deactivators, for example, NN disalicylidene ethylenediamine, may also be incorporated in the impregnating composition in proportions of up to 0.2% oxidation inhibitor and 0.02% metal deactivator by weight on the weight of the final composition, to prevent oxidation or deterioration of the composition both during manufacture and in the finished cable or condenser.

The invention includes a process for the manufacture of a composition for cable and condenser impregnation as above described, which process comprises dissolving polyisobutylene and/ or polyethylene in a synthetic hydrocarbon wax preferably in an inert atmosphere with agitation at an elevated temperature and thereafter adding petrolatum to the mixture. Alternatively using tht method of manufacture given in British patent specifica tion No. 650,088 the polyisobutylene may be dissolvei in a solvent and a mixture of petrolatum andsyntheti hydrocarbon wax added thereto, the solvent then bein removed.

The invention also includes cables and condensers th fibrous insulating layer-s whereof are impregnated with composition as above described.

The following is a description by way of example impregnating compositions made in accordance with tl present invention.

[Example I] [15 by weight Super Hard Wax No. 105." 85% by weight yellow petroleum jelly B. P.

point 125 F.) The composition had a Ubbelohde drop point of 76 C ExampleUI] I 15% by weight Super Hard Wax No. 105. 42.5% by weight yellow petroleum jelly B. P.

point 125 F.) 42.5% by weight polyisobutylene.

proximately 1,200. The composition had a Ubbelohde drop point of 85 [Example III] by weight Super Hard Wax No. 10

(Melting pr (Melti:

(Melti Molecular weight [25% by Weight green petroleum jelly.

The composition had a Ubbelohde drop point of 94 Example[IV] II 15% by weight Super Hard Wax No. 105.

5% by weight polyethylene grade 200.

% by weight yellow petroleum jelly B. P.

point 125 F.)

(Mel

The composition had a Ubbelohde drop point of 73 Example[V] Ill 10% by weight Super Hard Wax No. 105.

5% by weight micro-crystalline wax. (Melting 1 by Weight yellow petroleum jelly B. P. (Me

point 125 F.)

0 about 600, a melting point between 108 and 110 a boiling point under atmospheric pressure of 460 C., and low dielectric loss, together with from 1 ant to 40 percent by weight of at least one compound 12. A composition as set forth in claim 1.], and in- :lec'ted from the group consisting of polyisobutylene eluding from 1 percent to 40 percent by weight of rosin. aving a molecular weight of approximately 100,000 and 13. A composition as set forth in claim 11, and in- )lyethylene having a molecular weight of approximately eluding up to 0.02 percent by weight of NN disalicyl- 500.] 5 idene ethylenediamine.

[2. A composition as set forth in claim 1, and includ- 14. A composition as set forth in claim 11, and ing from 1 percent to 40 percent by weight of rosin] eluding up to 0.2 percent by weight of an oxidation in- [3. A composition as set forth in claim 1, and includhibitor.

g up to 0.02 percent by weight of NN disalicylidene 15. A process for the manufacture of a composition iylenediamine] for cable impregnation which process consists in dissolv- [4. A process for the manufacture of a composition ing from 1 percent to 40 percent by weight of at least r cable impregnation which process consists in dissolvone compound selected from the group consisting of g from 1 percent to 40 percent by weight of at least olyisobutylene having a molecular weight of approxie compound selected from the group consisting of polymately 1200 to 100,000 and polyethylene having a butylene having a molecular weight of approximately molecular weight of at least approximately 2,500, in 0,000 and polyethylene having a molecular Weight of from 3 percent to 50 percent by weight of a synthetic proximately 2,500, in from 3 percent to 50 percent Fischer Tropsch hydrocarbon wax having a molecular weight of a synthetic Fischer Tropsch hydrocarbon weight of approximately 600, a melting point between it having a molecular weight of approximately 600, 108 and 110 C., and low dielectric loss in an inert atnelting point between 108 and 110 C., and low dimosphere with agitation at a temperature from 110 to :tric loss in an inert atmosphere with agitation at a 140 C., and thereafter adding petrolatum to the mixlperature from 110 to 140 C., and thereafter addtare.

petrolatum to the mixture] 16. A composition for the impregnation of fibrous mo- :5. A composition as set forth in claim 1, and including terial for the insulation of the conductors of cables to 0.2 percent by weight of an oxidation inhibitor] which composition consists of solid petrolatum contain- A composition for the impregnation of fibrous maing from 3 percent to 50 percent by weight of a synthetic 1] for the insulation of the conductors of cables which Fischer Tropsch hydrocarbon wax having a melting point zposition consists of solid petrolatum containing from between 85 and 110 C., a boiling point under atmoszrcent to 50 percent by weight of a synthetic Fischer pheric pressure of above 46 C., and low dielectric loss, Dsch hydrocarbon Wax having w melting P n together with from 1 percent to 40 percent by weight of an 85 and 120 C., a boiling point under attmos at least one compound selected from the group consist- 'ic pressure of above 460" C., and low dielectric loss, ing of polyisobutyleiue having a molecular weight of apther with from 1 percent to 40 percent by weight proximately 1200 to 100,000 and polyethylene having a t least one compound selected from the group conmolecular weight of at least approximately 2,500.

1g of polyisobutylene having a molecular weight of 17. A composition as set forth in claim 16, and inoximately 1200 to 100,000 and polyethylene having eluding from 1 percent to percent by weight of rosin. olecular weight of at least approximately 2,500. 7 18. A composition as set forth in claim 16, and in- A composition as set forth in claim 6, and includeluding up to 0.02 percent by weight of NN disalicylram 1 percent to 40 percent by weight of rosin. idene ethylenediamine.

A composition as set forth in claim 6, and includ- 40 19. A composition as set forth in claim 16, and intp to 0.02 percent by weight of NN disalicylia'ene cluding up to 0.2

percent by weight of an oxidation inenediamine. hibitor. A MP 'I 0S s forth in im 6, and includ- 20. A process for the manufacture of a composition p to 0.2 percent by weight of an oxidation inhibitor. or cable impregnation which process consists in dissolv- A process for the manufacture of a composition ing from 1 percent to 40 percent by weight of at least able impregnation which process consists in dissolvone compound selected from the group consisting of "0m 1 percent to 40 percent by weight of at least olyisobu'tylene having a molecular weight of approxi- 2011117010161 selected from: the group consisting of mately 1200 to 100,000 and polyethylene having a molecrobutylene having a molecular weight of approxiular weight of at, least approximately 2,500, in from 3 y 1200 to 100,000 and polyethylene having a percent to 50 percen *ular weight of at least approximately 2.500, in Tropsch hydrocarbo 3 percent to 50 percent by weight of a synthetic tween and C., and low dielectric loss in an inert 2r Tropsch hydrocarbon wax having a melting point atmosphere with agitation at a temperature from 110" to en 85 and C., and low dielectric loss in an C., and thereafter ridding solid petrolatum to the atmosphere with agitation at a temperature from 55 mixture.

to 140 C., and thereafter adding solid petrolatum mixture. References Cited in the tile of this patent A composition for the impregnation of fibrous maor the original patent or the insulation of the conductors of cables which UNITED STATES PATENTS sition consists of petrolatum containing from 3 60 t to 50 percent by weight of a synthetic Fischer 1594829 Gray 1926 h hydrocarbon wax having a molecular weight of 1706333 Toch 1929 500, a melting point between 108 and 110 C., 2499756 Jacobson 1950 'ng point under atmospheric pressure of above 2551O87 Bgmhart et May 1951 7., and low dielectric loss, together with from 1 65 2536345 19; 1952 to 40 percent by weight of at least one com- 2594547 Fischer 1952 selected from the group consisting of polyisobutylg Pamlct 1952 ing a molecular weight of approximately 1200 to Thompson et 1958 l and polyethylene having a molecular weight of approximately 2,500, 

